[Dovecot] Command died with signal 6

Hi,

We have dovecot 1.1.20 running on Fedora 7 with mail and indexes on NFS. On our delivery server we are getting "status=bounced (Command died with signal 6: "/usr/local/libexec/dovecot/deliver")" We are fetching these mails from another server which has Centos 5.2 installed. We have mail_nfs*=yes and mmap_disable=yes settings in dovecot.conf.

Please let me know why the above error coming in dovecot logs?

Regards, Gourav Joshi